With the growing development of Internet, particularly, with the rise of the number of users, the increasing demand on bandwidth and the popularization of cloud service mode, it is more difficult for the traditional Metro convergence network to handle the requirements demanded by services on bandwidth, such as high flexibility, high reliability and low power consumption. Under this condition, OBRing, as an all-optical networking technology capable of providing sub-wavelength switching granularity, receives extensive attention and study. As shown in FIG. 1, OBRing generally can adopt a two-fibre self-healing ring form that is commonly used in a ring networking technology, and can support APS. The fibre channels of the OBRing are divided into a control channel and a data channel, in which the control channel is configured to transfer signalling on a control plane and to realize dynamic bandwidth allocation, management and configuration, and the like. The core of the OBRing lies in providing granularity based on the sub-wavelength bandwidth of an OB packet and all-optical switching capability, while bandwidth allocation and resource scheduling, protection switching and service recovery are two key technologies of the OBRing control plane. The protection switching and service recovery technology are the basis for improving network survivability and ensuring network availability.
The inherent feature of the ring topology enables a network to automatically enter a protection mode through a protection switching operation when the network encounters a failure, and tries to provide maximum available bandwidth by making use of remaining network connectivity and minimize the service interruption time until the network recovers to the normal working state after the fault repair.
If the Metro optical network is to employ the ring network protection switching, there are some examples in existing technical schemes: the Synchronous Digital Hierarchy (SDH) ring technology employs a self-healing ring technology, which includes two-fibre unidirectional (bidirectional) MS protection rings, two-fibre unidirectional (bidirectional) shared channel protection rings and the like, of which the basic principle is to network using two fibres or more fibres, make redundant resources as a reserved protection channel to form a 1:1 or N:1 protection; the resilient packet ring standards regulate some protection switching schemes such as wrapping mode, steering mode and cut-through mode; further, the Optical Transport Network (OTN), Packet Transport Network (PTN) and other networks have their own protection switching mechanisms. However, the above technical schemes are designed for respective network architecture, none of which can be directly available to the OBRing. From the view of technology, in the existing ring protection switching technical schemes, basic network design is that a node can perform photoelectric conversion on both services and control signals; however, in the OBRing only the control channel can perform photoelectric conversion, data service can pass through nodes transparently only, besides uplink and downlink; therefore, any protection switching method to schedule services in an electrical domain cannot be directly applied to the OBRing.
In the existing ring network technologies supporting protection switching, resilient packet ring is most close to the OBRing network model. In the steering mode protection switching of the resilient packet ring, a default node can perform photoelectrical conversion of services by default, thus switching scheduling is simple, however this protection switching mode still cannot be directly applied to the OBRing network, particularly for the centrally-controlled OBRing; the control information of bandwidth allocation needs a path to traverse all nodes one time and finally to return to the master node; however, the traditional steering mode based on distributed control does not take this condition into consideration. Actually, the cut-through mode is designed for the node capable of performing photoelectrical conversion too, this node can be crossed directly in the electrical domain in the case of electrical domain processing fault, thereby ensuring the remaining nodes in the network to continue working; however, in the OBRing the node itself supports the transparent pass-through of services, and only the control channel performs photoelectrical conversion; thus, the cut-through mode makes little sense to the OBRing. Wrapping mode, similar to the two-fibre unidirectional MS protection technology in SDH, completes conversion in the electrical domain only, which not only supports the photoelectrical optical network, but also supports all-optical networking technology; however, existing technical schemes related to the wrapping component still are not improved against the feature of the centrally-controlled OBRing; moreover, the wrapping mode in the all-optical switching OBRing will cause the transceiver on the spare fibre to enter a protection mode and thus to stop data transceiving, thereby leading to resource waste; therefore, the wrapping mode is not an optimized scheme in view of service recovery.
At present, there is no solution for protection switching and service recovery in the centrally-controlled OBRing all-optical switching network capable of providing sub-wavelength switching granularity.